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Message-ID: <e54d667c-58a5-4456-dda8-3a01d25c2489@nfschina.com>
Date:   Tue, 10 Oct 2023 09:20:13 +0800
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Subject: Re: [PATCH] fs/9p/xattr.c: avoid format-overflow warning
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To:     Christian Schoenebeck <linux_oss@crudebyte.com>, ericvh@kernel.org,
        lucho@ionkov.net, asmadeus@codewreck.org, v9fs@lists.linux.dev
Cc:     linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org
From:   Su Hui <suhui@nfschina.com>
In-Reply-To: <13910281.Zj71IQSfG8@silver>
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On 2023/10/10 02:34, Christian Schoenebeck wrote:
> On Sunday, October 8, 2023 8:01:39 AM CEST Su Hui wrote:
>> with gcc and W=1 option, there's a warning like this:
>>
>> In file included from fs/9p/xattr.c:12:
>> In function ‘v9fs_xattr_get’,
>>      inlined from ‘v9fs_listxattr’ at fs/9p/xattr.c:142:9:
>> include/net/9p/9p.h:55:2: error: ‘%s’ directive argument is null
>> [-Werror=format-overflow=]
>>     55 |  _p9_debug(level, __func__, fmt, ##__VA_ARGS__)
>>        |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> use "" replace NULL to silence this warning.
>>
>> Signed-off-by: Su Hui <suhui@nfschina.com>
>> ---
>>   fs/9p/xattr.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/fs/9p/xattr.c b/fs/9p/xattr.c
>> index e00cf8109b3f..d995ee080835 100644
>> --- a/fs/9p/xattr.c
>> +++ b/fs/9p/xattr.c
>> @@ -139,7 +139,7 @@ int v9fs_fid_xattr_set(struct p9_fid *fid, const char *name,
>>   
>>   ssize_t v9fs_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
>>   {
>> -	return v9fs_xattr_get(dentry, NULL, buffer, buffer_size);
>> +	return v9fs_xattr_get(dentry, "", buffer, buffer_size);
>>   }
>>   
>>   static int v9fs_xattr_handler_get(const struct xattr_handler *handler,
>>
> Mmm, that's not the same is it? Have you tested this change?
Oh, sorry.  That's not the same and I just tested compilation.
>
> Currently this function causes a 'Txattrwalk' 9p message to be sent to 9p
> server with its name[s] field being NULL, and the latter being the magical
> hint to 9p server to not send an attribute, but rather the list of attributes.
>
> With your change I would assume that it would rather ask server for one
> attribute called "". I have not tested myself, just worrying that it might
> break behaviour.
Got it, I made a mistake there. Thanks for your explanation.
Sorry for the noise again.

Su Hui